Turn off EL, drain water and take CW side apart and pull out dip tube, if it is to long you will have to take HW apart and lean tank over to get tube out. The lower el. you need a 1-5/8″ socket are maybe bigger are smaller to take it out, if you dont have tools you might get a Lic. Plumber to do it.
Could be a faulty element or thermostat. Alternatively, are you sure you are not draining the water heater? Check the flow rate of the shower if it is too high install a flow regulator or replace the showerhead with a watersaving one.
Also the bottom of tank could be full of sediment. Turn off EL, drain tank take out lower EL. and see if it is got sediment in if so loosen it up in tank and take piece of 3/4″ pvc pipe about 18″ long and use a wet vac and suck it out check element see if it is good.